green screen object

how can I put and video and limit the frames of the video into the "moving green object".
like in this video:
pause at 00:49 to see how the glasses are made. and how will the "+" markers help me?
or do I have to do it each frame in sec fps
Can it all be done in sony vegas?

I'm not familiar with this sort of thing to advise you. I just know masking you have to click around the edge of the image. You might want to look up rotoscoping as well. Vegas will do this kind of thing but it's a lot of work. After effects is more the sort of thing to use which is probably what this example was done with.